1. Unit III - Acid/Base - Chapter 15

2. 15. x. Relate [H+], [OH-], and Kw in an aqueous solution. [Readings 17
15.x. Relate [H+], [OH-], and Kw in an aqueous solution. [Readings 17.2,17.6 Problems 2]

3. 15.1. Define acids and bases in terms of Arrhenius and Brönsted-Lowry theories and identify the conjugate acid-base pairs. [Readings Problems]

4. Arrhenius Theory of Acids/Bases
Acid -- H+ in water solution
Base -- OH- in water solution
Works well for substances like NaOH and HCl
What about NH3?

5. Brönsted-Lowry Theory of Acids/Bases (1923)
Acid -- Proton Donor
Base -- Proton Acceptor

6. HCl (aq) <=> H+ (aq) + Cl- (aq) -or-
Hydrolysis Reactions
HCl (aq) <=> H+ (aq) + Cl- (aq)
-or-
H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq)
acid hydrolysis
HCl is the proton donor, thus the acid
H2O is the proton acceptor, thus, the Bronsted-Lowry base

7. Conjugate Acid-Base Pairs
H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq)
Species that differ only by a proton are conjugates of each other
Cl - is the conjugate base of HCl
H2O is the conjugate base of H3O+

8. Practice Write the balanced equation of NH3 dissolving in water.
NH3 + H2O ––> NH OH-
Identify the conjugate acid-base pair
H2O and OH-
Identify the conjugate base-acid pair
NH3+ and NH4+

9. Auto Ionization of water
H2O(l) <==> H+(aq) + OH-(aq)
Kw = [H+] [OH-] = 1.0 x @ 25°C
in pure water [H+] = [OH-] = 1.0 x 10-7 M
at this concentration only one water molecule in 556 million is ionized.

10. [H+] = 10-7 M neutral [OH-] = 10-7 M
Kw = [H+] [OH-] = 1.0 x 10-14
[H+] = 10-7 M neutral [OH-] = 10-7 M
increase [H+]
[H+] > 10-7 M acid [OH-] < 10-7 M
increase [OH-]
[H+] < 10-7 M base [OH-] > 10-7 M

11. What is the nature of H+(aq)
Hydronium Ion H O H O +    H H - O O H H 

12. Alternative View H O 
hydrated proton +  H
H3O hydronium ion

13. H+ H3O+
H2O(l) <==> H+(aq) + OH-(aq)
Kw = [H+] [OH-] = 1.0 x @ 25°C
H2O(l) + H2O(l) <==> H3O+(aq) + OH-(aq)
Kw = [H3O+] [OH-] = 1.0 x @ 25°C

14. Why Not....
H5O2+ H O + H O H

15. Why Not....
H7O3+ . H O + H H O H O H O H

16. 3.2. Determine the pH of an aqueous solution from the [H+] (or the [OH-]) and vv. [Readings 17.6 Problems 32,34,36]

17. pH - a shorthand method of expressing [H+] of dilute solutions
pH = -log [H+]
pH of pure water? [H+]=1x10-7
pH = -log (1x10-7)
pH = 7

18. Kw = [H+] [OH-] = 1.0 x 10-14
[H+] = 10-7 M; pH = 7
neutral

19. What is the pH of a [OH-] = 1.8 x 10-5?
[H+] = Kw / [OH-]
pH = -log [H+]
Answer 9.26

20. Kw = [H+] [OH-] = 1.0 x 10-14
[H+] = 10-7 M; pH = 7
neutral
[OH-] > 10-7 M; [H+] < 10-7 M; pH >7
Base

21. If the pH of a solution= 2.6; what is the [H+]?
Answer 2.5 x 10-3 M

22. Kw = [H+] [OH-] = 1.0 x 10-14
[H+] = 10-7 M; pH = 7
neutral
[OH-] > 10-7 M; [H+] < 10-7 M; pH >7
Base
[H+] > 10-7 M; [OH-] < 10-7 M; pH <7
Acid

23. Effective pH Range
0-7 --Acid
7 -- Neutral
Base
What is the pH of a 2 M [H+]?
Answer

24. 3. 4. Recognize and construct conjugates of acids or bases
3.4. Recognize and construct conjugates of acids or bases. [Readings 17.3 Problems 12,18,20]

25. Conjugates
H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq)
acid
base

26. H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq) acid base
Conjugates
H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq)
acid
base
Conjugates

27. H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq) acid base
Conjugates
H2O + HCl (aq) <=> H3O+ (aq) + Cl- (aq)
acid
base
Conjugates

28. The Hydrolysis of Benzoic Acid
HC7H5O2
Write the equation.
HC7H5O2(aq) + H2O(l) <==> H3O+ (aq) + C7H5O2 -(aq)
Identify acids, bases, and conjugates.

29. The Hydrolysis of Benzoic Acid
HC7H5O2
Write the equation.
HC7H5O2(aq) + H2O(l) <==> H3O+ (aq) + C7H5O2 -(aq)
Identify acids, bases, and conjugates.
Base
Acid
conjugate

30. The Hydrolysis of Benzoic Acid
HC7H5O2
Write the equation.
HC7H5O2(aq) + H2O(l) <==> H3O+ (aq) + C7H5O2 -(aq)
Identify acids, bases, and conjugates.
Base
Acid
conjugate

31. The Hydrolysis of Ammonia
NH3 is a base.
H2O(l) + NH3(aq) <==> NH4+ (aq)+ OH-(aq)

32. The Hydrolysis of Ammonia
NH3 is a base.
H2O(l) + NH3(aq) <==> NH4+ (aq)+ OH-(aq)
Acid
Base

33. The Hydrolysis of Ammonia
NH3 is a base.
H2O(l) + NH3(aq) <==> NH4+ (aq)+ OH-(aq)
H2O(l) as acid or base.
Acid
Base

34. The Hydrolysis of Ammonia
NH3 is a base.
H2O(l) + NH3(aq) <==> NH4+ (aq)+ OH-(aq)
H2O(l) as acid or base.
Base Hydrolysis
Acid
Base

35. 3. 5. Determine the [H+] and pH of a strong acid or base solution
3.5. Determine the [H+] and pH of a strong acid or base solution. [Readings 17.4 Problems 34]

36. Hydrolysis of HCl H2O + HCl (aq) --> H3O+ (aq) + Cl- (aq)
I M M M
pH = 1.0
F M M M
K = large - Strong Acid
conjugate Cl- -- according to B/L is a base

37. 3.6. Determine and relate equilibrium concentrations, [H+], pH and Ka values for weak acids (also, same for Kb values for weak bases). [Readings 17.5 Problems 40,42,44]

38. Hydrolysis of HC7H5O2
H2O + HC7H5O2 (aq) <==> H3O+ (aq) + C7H5O2 - (aq)
I M M M
pH = 2.6
C M M M
E M M M
KA = [H3O+] [C7H5O2 - ] / [HC7H5O2 ] = 6.4 x Weak Acid
conjugate C7H5O according to B/L is a base

39. Strong Acids vs. Weak Acids
Strong Acids: HCl, HBr, HI, H2SO4, HNO3, HClO4
Strength is a measure of the extent of dissociation.
Conjugates of weak acids are weak bases (v.v.). Conjugates of strong acids (or bases) are neutral.
Examples of weak acids:
Molecules -- HC2H3O2
Anions -- HSO4-
Cations -- NH4+
Fe+3

40. Strong Bases vs. Weak Bases
Strong Base: NaOH (s) --> Na+ (aq) + OH- (aq) K = 
Strong Bases: hydroxides of group I and II.
Weak Base: C5H5N (aq) + H2O <==> C5H5N H+ (aq) + OH-(aq) KB = [C5H5N H+] [OH-] / [C5H5N] = 1.7 x 10 -9
Examples of weak bases: Molecules -- NH Anions -- F-
Tables of values of KA and KB -- see page A20-22.

41. 3.7. Determine the [H+] and pH of weak acids or bases from initial concentrations. [Readings 17.7 Problems 46,48,50]

42. What is the pH of a 1.0 M solution of C5H5N?
Is C5H5N acid or base, weak or strong?
If strong acid (e.g. HCl) pH =0
If strong base (e.g. NaOH) pH =14
Must be weak! Look on KA and KB tables.
KB = 1.7 x 10 -9

43. 3.8. Construct an ordered list of strongest to weakest (or vv) acids or bases. [Readings 17.3 Problems 22,24,26]

44. Acid/Base Relative Strengths
In water solutions all strong acids are equally strong and all strong bases are equally strong.
Weak acids and bases have relative strengths measured by their equilibrium constants.
The stronger the acid or base the weaker the conjugate.

45. Example Problem HI, K+, HC2H3O2, H2O2, HNO2
Rank the following in order of acid strength from largest to smallest.
HI, K+, HC2H3O2, H2O2, HNO2

46. 3.9. Determine the Kb for a weak base, given the Ka value of its conjugate acid (vv). [Readings 17.6 Problems 66]

47. Conjugate KA, KB relationships
HCN (aq) + H2O (l) <==> H3O+ (aq) + CN- (aq) KA=6.2x10-10
CN- (aq) + H2O (l) <==> OH- (aq) + HCN (aq) KB=?
______________________________________
2 H2O (l) <==> H3O+ (aq) + OH- (aq) Kw=1.0x10-14
KA = [H3O+ ] [CN-] / [HCN ] KB = [OH-] [HCN ] / [CN-] Kw = [H3O+] [OH-]
[H3O+ ] [CN-] / [HCN ] x [OH-] [HCN ] / [CN-] = [H3O+] [OH-]
therefore: KA KB = Kw ; KB = Kw / KA
KB = 1.0x10-14 / 6.2x10-10 = 1.6x10-5

48. 3. 11. Qualitatively determine the acidic or basic properties of salts
3.11. Qualitatively determine the acidic or basic properties of salts. [Readings 17.8 Problems 60,61]

49. The interaction of acids and bases
Acid + Base --> Salt + Water
SA SB
WA SB
SA WB
WA WB

50. Examples:
Strong Weak
Acid HCl HCN; KA= 6.2x10-10
Base NaOH NH3; KB= 1.8x10-5

51. Strong Acid + Strong Base
NaOH + HCl --> NaCl + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCl --> H3O+ + Cl-
SA N

52. Strong Acid + Strong Base
NaOH + HCl --> NaCl + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCl --> H3O+ + Cl-
SA N

53. Strong Acid + Strong Base
NaOH + HCl --> NaCl + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCl --> H3O+ + Cl-
SA N

54. Strong Acid + Strong Base
NaOH + HCl --> NaCl + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCl --> H3O+ + Cl-
SA N
NaCl -- Neutral Salt

55. The interaction of acids and bases
Acid + Base --> Salt + Water
SA SB N
WA SB
SA WB
WA WB

56. Weak Acid + Strong Base
NaOH + HCN --> NaCN + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCN --> H3O+ + CN-
WA WB

57. Weak Acid + Strong Base
NaOH + HCN --> NaCN + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCN --> H3O+ + CN-
WA WB

58. Weak Acid + Strong Base
NaOH + HCN --> NaCN + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCN --> H3O+ + CN-
WA WB

59. Weak Acid + Strong Base
NaOH + HCN --> NaCN + H2O
NaOH --> Na+ + OH-
SB N
H2O + HCN --> H3O+ + CN-
WA WB
NaCN -- Basic Salt

60. The interaction of acids and bases
Acid + Base --> Salt + Water
SA SB N
WA SB B
SA WB
WA WB

61. Strong Acid + Weak Base
NH3 + HCl --> NH4Cl
H2O + NH3 --> NH4+ + OH-
WB WA
H2O + HCl --> H3O+ + Cl-
SA N

62. Strong Acid + Weak Base
NH3 + HCl --> NH4Cl
H2O + NH3 --> NH4+ + OH-
WB WA
H2O + HCl --> H3O+ + Cl-
SA N

63. Strong Acid + Weak Base
NH3 + HCl --> NH4Cl
H2O + NH3 --> NH4+ + OH-
WB WA
H2O + HCl --> H3O+ + Cl-
SA N

64. Strong Acid + Weak Base
NH3 + HCl --> NH4Cl
H2O + NH3 --> NH4+ + OH-
WB WA
H2O + HCl --> H3O+ + Cl-
SA N
NH4Cl -- Acidic Salt

65. The interaction of acids and bases
Acid + Base --> Salt + Water
SA SB N
WA SB B
SA WB A
WA WB

66. Weak Acid + Weak Base
NH3 + HCN --> NH4CN
H2O + NH3 --> NH4+ + OH-
WB WA KB= 1.8x KA= 5.6x10-10
H2O + HCN --> H3O+ + CN-
WA WB KA= 6.2x KB= 1.6x10-5

67. Weak Acid + Weak Base
NH3 + HCN --> NH4CN
H2O + NH3 --> NH4+ + OH-
WB WA KB= 1.8x KA= 5.6x10-10
H2O + HCN --> H3O+ + CN-
WA WB KA= 6.2x KB= 1.6x10-5

68. Weak Acid + Weak Base
NH3 + HCN --> NH4CN
H2O + NH3 --> NH4+ + OH-
WB WA KB= 1.8x KA= 5.6x10-10
H2O + HCN --> H3O+ + CN-
WA WB KA= 6.2x KB= 1.6x10-5

69. Weak Acid + Weak Base
NH3 + HCN --> NH4CN
H2O + NH3 --> NH4+ + OH-
WB WA KB= 1.8x KA= 5.6x10-10
H2O + HCN --> H3O+ + CN-
WA WB KA= 6.2x KB= 1.6x10-5
NH4CN -- Basic Salt

70. The interaction of acids and bases
Acid + Base --> Salt + Water
SA SB N
WA SB B
SA WB A
WA WB depends on relative strengths

71. Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2-

72. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2-
Conjugate
NaOH

73. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2-
Conjugate
NaOH SB

74. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2- N
Conjugate
NaOH SB

75. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2- N
Conjugate
Conjugate
NaOH SB
HCHO2

76. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2- N
Conjugate
Conjugate
NaOH SB
HCHO2 WA

77. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2- N B
Conjugate
Conjugate
NaOH SB
HCHO2 WA

78. Sodium Formate -- NaCHO2 NaCHO2 --> Na+ + CHO2-
Self Test
Sodium Formate -- NaCHO2
NaCHO2 --> Na+ + CHO2- B N B
Conjugate
Conjugate
NaOH SB
HCHO2 WA

79. Self Test
Sodium Nitrate -- NaNO3
NaNO3 --> Na+ + NO3-

80. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- NaOH
Conjugate
NaOH

81. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- NaOH SB
Conjugate
NaOH SB

82. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- N NaOH SB
Conjugate
NaOH SB

83. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- N NaOH SB
Conjugate
Conjugate
NaOH SB
HNO3

84. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- N NaOH SB
Conjugate
Conjugate
NaOH SB
HNO3 SA

85. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- N N NaOH SB
Conjugate
Conjugate
NaOH SB
HNO3 SA

86. Self Test Sodium Nitrate -- NaNO3 NaNO3 --> Na+ + NO3- N N N NaOH
Conjugate
Conjugate
NaOH SB
HNO3 SA

87. Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br -

88. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br -
Conjugate
NH3

89. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br -
Conjugate
NH3 WB

90. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br - A
Conjugate
NH3 WB

91. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br - A
Conjugate
Conjugate
NH3 WB
HBr

92. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br - A
Conjugate
Conjugate
NH3 WB
HBr SA

93. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br - A N
Conjugate
Conjugate
NH3 WB
HBr SA

94. Ammonium Bromide -- NH4Br NH4Br--> NH4+ + Br -
Self Test
Ammonium Bromide -- NH4Br
NH4Br--> NH4+ + Br - A A N
Conjugate
Conjugate
NH3 WB
HBr SA

95. 3. 10. Determine the pH of a salt solution. [Readings 17
3.10. Determine the pH of a salt solution. [Readings 17.8 Problems 62,64]

96. What is the pH of a solution of 3.45 g of NaNO2 in 250 mL of solution?

97. 3. 12. Identify acids and bases using Lewis theory. [Readings 17
3.12. Identify acids and bases using Lewis theory. [Readings Problems 74]

98. Self Test
Iron (III) Chloride -- FeCl3
FeCl3 --> Fe+3 + 3Cl-

99. Iron (III) Chloride -- FeCl3 FeCl3 --> Fe+3 + 3Cl-
Self Test
Iron (III) Chloride -- FeCl3
FeCl3 --> Fe+3 + 3Cl-
Conjugate
HCl

100. Iron (III) Chloride -- FeCl3 FeCl3 --> Fe+3 + 3Cl-
Self Test
Iron (III) Chloride -- FeCl3
FeCl3 --> Fe+3 + 3Cl-
Conjugate
HCl SA

101. Iron (III) Chloride -- FeCl3 FeCl3 --> Fe+3 + 3Cl-
Self Test
Iron (III) Chloride -- FeCl3
FeCl3 --> Fe+3 + 3Cl- N
Conjugate
HCl SA

102. Iron (III) Chloride -- FeCl3 FeCl3 --> Fe+3 + 3Cl-
Self Test
Iron (III) Chloride -- FeCl3
FeCl3 --> Fe+3 + 3Cl- N
Conjugate
Conjugate ?
HCl SA

103. Fe+3 tests as an acid +3 Fe .. O .. H  High Charge to Size Ratio
Al+3, Fe+3 are two best examples H O .. .. 

104. Lewis Theory of Acids and Bases
Acid -- Electron Pair Acceptor
Base -- Electron Pair Donor
C N - . A l + 3

105. Comparing Theories H + O - : . . . + - H : O H . . . . + - H : O H . .
B/L Theory
Lewis . .
Arrhenius + - H : O H . . . . + - H : O H . .

106. 3. 13. Determine the pH of weak and strong polyprotic acids
3.13. Determine the pH of weak and strong polyprotic acids. [Readings 17.9 Problems 72]

107. Self Test
Sodium Bicarbonate -- NaHCO3
NaHCO3 --> Na+ + HCO3-

108. Sodium Bicarbonate -- NaHCO3 NaHCO3 --> Na+ + HCO3-
Self Test
Sodium Bicarbonate -- NaHCO3
NaHCO3 --> Na+ + HCO3-
Conjugate
NaOH

109. Sodium Bicarbonate -- NaHCO3 NaHCO3 --> Na+ + HCO3-
Self Test
Sodium Bicarbonate -- NaHCO3
NaHCO3 --> Na+ + HCO3-
Conjugate
NaOH SB

110. Sodium Bicarbonate -- NaHCO3 NaHCO3 --> Na+ + HCO3-
Self Test
Sodium Bicarbonate -- NaHCO3
NaHCO3 --> Na+ + HCO3- N
Conjugate
NaOH SB

111. Sodium Bicarbonate -- NaHCO3 NaHCO3 --> Na+ + HCO3-
Self Test
Sodium Bicarbonate -- NaHCO3
NaHCO3 --> Na+ + HCO3- N
Conjugate
Conjugate
NaOH SB ?

112. HCO Acid or Base?
HCO3- + H2O <==> H3O+ + CO3-2
HCO3- + H2O <==> H2CO3 + OH-

113. HCO3- + H2O <==> H3O+ + CO3-2
HCO Acid or Base?
HCO3- + H2O <==> H3O+ + CO3-2
HCO3- + H2O <==> H2CO3 + OH- H O C

114. HCO3- + H2O <==> H3O+ + CO3-2
HCO Acid or Base?
HCO3- + H2O <==> H3O+ + CO3-2
HCO3- + H2O <==> H2CO3 + OH-
KA2 = 5.6 x 10-11
KB = Kw / KA1 = 1 x / 4.3 x 10-7 = 2.3 x 10-8 H O C

115. H2CO3 + H2O <==> H3O+ + HCO3-
Polyprotic Acids
H2CO3 + H2O <==> H3O+ + HCO3-
HCO3- + H2O <==> H3O+ + CO3-2
KA1 = 4.3 x 10-7
KA2 = 5.6 x 10-11

116. What is the pH of Polyprotic Strong Acids
H2SO4 + H2O --> H3O+ + HSO4- KA1 = large
HSO4- + H2O --> H3O+ + SO KA2 = 1.2 x 10-2
Depends on Concentration-- if 1M the second H+ makes almost no difference at lower concentrations second H+ makes a larger contribution

117. What is the pH of Polyprotic Weak Acids
H3PO4 + H2O --> H3O+ + H2PO4- KA1 = 7.5 x 10-3
H2PO4- + H2O --> H3O+ + HPO4-2 KA2 = 6.2 x 10-8
HPO H2O --> H3O+ + PO KA3 = 4.8 x 10-13
Second H+ makes almost no difference